2. amps-preamps
  3. 177110-5705

Tube or Amp Problem? Please help.

I have a Melody El34 Integrated Amp that I use with 2 pairs of Shuguang Treasure 6CA7-z. Last week I was listening to music when everything went all horrible sounding and one of the tubes lit up like blue fireworks. I turned off the amp and looked at it the next day. To my, admittedly untrained eye, the tube looks fine but when I checked the bias it was at .32 (the amp says to set to .40) so I tried to set it to .40 but it would only go to .34. All of the other tubes I can set to .40. I have never had this issue with this amp. Is it the tube or did something happen to the amp? If it's just the tube will it be ok to have one set to .34 and the other .4 or should I set both tubes to .34, all 4? I would buy a new pair but they were expensive and on top of that don't seem to be offered anymore.

128x128jkontuly
lowrider57's avatar
lowrider57
5,417 posts
 

@jkontuly if the bias pot had range when turning left and right, then the amp is ok. However, you want to make sure that bias will remain steady and not drift.

tuberist
951 posts
 

This happens with tubes sometimes that’s why we keep spares

jkontuly's avatar
jkontuly OP
59 posts
 

Given that I can set the bias for each tube individually is it still important that I replace both on the side that this occurs...I still plan on doing this but just more for my own education.

russ69's avatar
russ69
3,501 posts
 

Given that I can set the bias for each tube individually is it still important that I replace both on the side that this occurs

Although the bias is independent the circuit is designed to have a pair of matched tubes. 

artemus_5's avatar
artemus_5
1,926 posts
 

Given that I can set the bias for each tube individually is it still important that I replace both on the side that this occurs...I still plan on doing this but just more for my own education.

Russ has given you the correct answer. And as others have said, its best to replace all of them if they have a lot of hours. FWIW you got lucky in that the tube didn't do more damage. I had a set of Shuguang Nature series in which one blew and $650 later my amp worked again. They sounded good but at a very high price. They were just getting broken in.

The Melody has a good reputation so if you like it then get some tubes. Here is some. Affordable too. Have fun

EL 34

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